SEARCH · PubMed Health

Results for “Astrocytes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed2006

Relevance of astrocytic activation to reductions of astrocytic GABAA receptors.

Although astrocytes express gamma-aminobutyric acid subtype-A (GABAA) receptors in the mature brain, GABAA receptor expression in a cultivation state remains controversial. In this study, we investigated the alteration of astrocytic GABAA receptor expression in in vitro and in vivo studies to elucidate the relevance of astrocytic activation to reductions of astrocytic GABAA receptors. The GABA-evoked Cl- current (GABAA response) in cultured astrocytes was determined by recording in the whole-cell mode using a conventional patch-clamp technique under voltage-clamp conditions. The respective amplitudes of GABAA responses on days in vitro 1, 3-5, 7-10, and 12-15 were 1019+/-97, 512+/-76, 84+/-21, and 22+/-9 pA, respectively, suggesting that the GABAA response subsequently diminished with in vitro aging. In immunohistochemical and biochemical analyses, the expression of GABAA receptor beta-subunit decreased, whereas expressions of glial fibrillary acidic protein (GFAP) and S100B, hallmarks of astrocytic activation, increased dramatically in the cultured astrocytes with in vitro aging. With the use of [3H]SR95531, a GABAA-specific ligand, at 24 h after transient focal ischemia, binding was significantly reduced in the astrocytic fractions without affecting the synaptosomal fractions, and decreases in the mRNA expression level of GABAA receptor beta-subunits were concurrently observed. Interestingly, the loss of GABAA response in cultured astrocytes was mitigated by co-culturing with neurons or treatments with monoclonal S100B antibodies. These results indicate that astrocytic GABAA receptors are reduced with in vitro aging and cerebral ischemia, presumably through the overproduction of S100B in activated astrocytes.

Aging↗

PubMed2004

Down's syndrome astrocytes have greater antioxidant capacity than euploid astrocytes.

Down's syndrome (trisomy 21) brain tissue is considered to be susceptible to oxidative injury, mainly because its increased Cu/Zn-superoxide dismutase (SOD1) activity is not followed by an adaptive rise in hydrogen peroxide metabolizing enzymes. In vitro, trisomic neurons suffer oxidative stress and degenerate. We studied the response of trisomy 21 neuron and astrocyte cultures to hydrogen peroxide injury and found that they were, respectively, more and less vulnerable than their euploid counterparts. Differences were detected 24 h after exposures in the region of 50 microm and 500 microm hydrogen peroxide for neuron and astrocyte cultures, respectively. Cytotoxicity results were paralleled by a decrease in cellular glutathione. In addition, trisomic astrocytes showed a lower basal content of superoxide ion and a higher clearance of hydrogen peroxide from the culture medium. In the presence of hydrogen peroxide, trisomic astrocytes maintained their concentration of intracellular superoxide and hydroperoxides at a lower level than euploid astrocytes. Consistent with these results, trisomic astrocytes in neuron coculture were more neuroprotective than euploid astrocytes against hydrogen peroxide injury. We suggest that SOD1 overexpression has beneficial effects on astrocytes, as it does in other systems with similarly high disposal of hydroperoxides. In addition to a higher enzymatic activity of SOD1, cultures of trisomic astrocytes showed slightly higher glutathione reductase activity than euploid cultures. Thus, trisomy 21 astrocytes showed a greater antioxidant capacity against hydrogen peroxide than euploid astrocytes, and they partially counteracted the oxidative vulnerability of trisomic neurons in culture.

Antioxidants↗

PubMed1996

Regulation of HIV-1 infection in astrocytes: expression of Nef, TNF-alpha and IL-6 is enhanced in coculture of astrocytes with macrophages.

'Restricted' human immunodeficiency virus type (HIV-1) infection of astrocytes is recognized in vivo in some pediatric and adult AIDS brains and in vitro in a small proportion of transfected primary fetal astrocytes. We investigated the extent of HIV-1JR-FL expression in fetal astrocytes and macrophages cultivated alone or together. Peak HIV-1 p24 antigen titres in supernatant fluids of macrophage cultures were increased with monocyte/macrophages from certain donors and were higher when macrophages were cocultivated with astrocytes. Structural HIV-1 gene (gp 41 and pol) products (protein and mRNA) were observed only in macrophages. Ten days after HIV-1JR-FL infection, astrocytes in a monoculture were stained negative or only weakly positive (1-2+) for Nef, whereas in a coculture up to 100% of astrocytes displayed Nef staining (up to 4+) in the cytoplasm. The streptavidine-biotine-peroxidase technique with certain monoclonal antibodies to Nef (Ovod et al, 1992) was specific for infected astrocytes. The intensity of Nef staining was higher in astrocytes cultivated with monocyte/macrophages from certain donors. In the coculture, tumor necrosis factor-alpha (TNF-alpha) was expressed in the astrocyte cytoplasm earlier after coinfection with HIV-1 and cytomegalovirus (CMV) compared to infection with HIV-1 alone. Interleukin-6 (IL-6) was secreted spontaneously and transiently in uninfected cocultures, but in a prolonged fashion following HIV-1 and HIV-1/CMV infections. The interactions between HIV-1- and CMV-infected macrophages and astrocytes lead to upregulation of TNF-alpha and IL-6 and enhancement of productive HIV-1 infection of macrophages and of 'restricted' HIV-1 infection of astrocytes with implications for the pathogenesis of AIDS dementia.

Astrocytes↗

PubMed1984

Astrocytic membrane morphology: differences between mammalian and amphibian astrocytes after axotomy.

Previous studies have shown that astrocytes in some nonmammalian species provide a favorable environment for axonal elongation, whereas mammalian astrocytes are thought to inhibit fiber outgrowth. The present study was performed to determine whether any plasma membrane differences exist between these glial elements which could account for their contrasting effects upon axonal outgrowth. Astrocytic scars were formed in optic nerves of rats, newts, and frogs by enucleation. Subsequently, the astrocytic membranes were examined with the freeze-fracture technique. Orthogonal arrays of small intramembranous particles (IMPs) are a prominent component of the plasma membranes of normal mammalian astrocytes; these arrays are most numerous in astrocytic membranes that form an interface between the CNS and nonneural tissue. Astrocytic membranes within the normal CNS parenchyma, however, possess much lower densities of arrays. Following axotomy and Wallerian degeneration, the density of arrays increased threefold within the parenchyma of the optic nerve, while remaining constant at the glia limitans. In striking contrast, only a few aggregates of IMPs that resembled orthogonal arrays could be found in normal and reactive astrocytes of amphibians, although the cytology of these glial cells and density of the scars are otherwise similar to those of their mammalian counterparts. These findings suggest (1) that a proliferation of orthogonal arrays in astrocytic plasma membranes is a prominent feature of gliosis in the mammalian CNS and (2) that differences in the composition of reactive mammalian and amphibian astrocytic membranes may account for variations in axonal-glial interactions within the injured CNS.

Aging↗

PubMed2006

Bone marrow stromal cells induce BMP2/4 production in oxygen-glucose-deprived astrocytes, which promotes an astrocytic phenotype in adult subventricular progenitor cells.

Bone morphogenetic proteins (BMPs) affect cell proliferation and differentiation. Astrocytes in ischemic brain are highly responsive to bone marrow stromal cell (BMSC) treatment. We investigated the effects of BMSCs on astrocytes cultured under oxygen- and glucose-deprived conditions, which in part simulate in vivo stroke conditions, to test the hypothesis that BMSCs alter astrocytic expression of BMPs which may contribute to neurological functional recovery of stroke. Quantitative real-time RT-PCR showed that the expression of BMP2/4 mRNAs decreased within ischemic astrocytes, In contrast, BMP2/4 mRNA was significantly increased after cocultured with BMSCs. Western blotting also confirmed this increase at the protein level in the medium of ischemic astrocytes after coculture with BMSCs. As a source of neural stem and progenitor cells, cultured subventricular zone (SVZ) neurospheres exposed to medium obtained from ischemic astrocytes cocultured with BMSCs were significantly enriched in cells expressing the astrocytic marker glial fibrillary acidic protein (GFAP), but not at the expense of beta-III-tubulin-positive SVZ neuroblasts. The expression of BMP2/4 subsequently increased the phosphorylation of downstream effector Smad1 and the expression of notch signal pathway-induced protein Hes1 in cultured SVZ neurospheres. BMP antagonist Noggin blocked the elevation of phosphorylated Smad1 and the expression of Hes1 as well as reducing the percentage of astrocytic SVZ progenitor cells. Our results indicate that BMSCs increase BMP2/4 expression in ischemic astrocytes. These changes enhance subventricular progenitor cell gliogenesis by activating relevant signaling pathways. BMSC-stimulated signaling of endogenous astrocytes may alter the ischemic environment, promoting remodeling of brain and hence, improve functional recovery after stroke.

Animals↗

PubMed1994

Type-2 astrocytes have much greater susceptibility to heat stress than type-1 astrocytes.

The present investigations were undertaken to examine the susceptibility of type-2 astrocytes to elevated temperature. Type-2 astrocytes are much more easily injured by temperature elevation than type-1 astrocytes. This may be related to cellular redox potential. Type-1 astrocytes have a greater cytosolic NAD redox potential (i.e., higher NADH:NAD levels) than type-2 astrocytes as evidenced by a 9-fold higher ratio of lactate to pyruvate released into the medium by type-1 astrocytes than type-2 astrocytes. Heat stress causes the induction of hsp-72 in both type-2 and type-1 astrocytes; however, hsp-72 protein expression is retained for a longer period of time by the type-2 astrocyte. A possible basis for the greater sensitivity of type-2 astrocytes to stress may be a poorer ability to scavenge free radicals. This differential sensitivity of one neural cell type relative to another to elevated temperature may be of significance in understanding the effects of hyperthermia on the developing brain.

Animals↗

PubMed2005

Bone marrow stromal cells increase astrocyte survival via upregulation of phosphoinositide 3-kinase/threonine protein kinase and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase pathways and stimulate astrocyte trophic factor gene expression after anaerobic insult.

Transplantation of bone marrow stromal cells improves animal neurological functional recovery after stroke. Astrocytes are known to provide structural, trophic and metabolic support for neurons. Thus astrocytes are critical for neural survival during post-ischemia. However, information on the effects of bone marrow stromal cells on astrocytic survival post-ischemia is unavailable. We investigated the influence of rat bone marrow stromal cells on rat astrocytic apoptosis and survival post-ischemia employing an anaerobic chamber. Our data indicate that rat bone marrow stromal cells reduce cell death and apoptosis, and increase the DNA proliferation rate in astrocytes post-ischemia. Mitogen-activated protein kinase kinase/extracellular signal regulated kinase and phosphoinositide 3-kinase/threonine protein kinase pathways are involved in cell survival. Western blot showed that rat bone marrow stromal cells activate these two pathways in astrocytes post-ischemia, and upregulate total extracellular signal regulated kinase 1/2 and threonine protein kinase. Since astrocytes produce various neurotrophic factors, we performed reverse transcription polymerase chain reaction to investigate rat bone marrow stromal cells' effect on astrocyte growth factor gene expression post-ischemia. We observed that brain-derived neurotrophic factor, vascular endothelial growth factor and basic fibroblast growth factor gene expression was enhanced by rat bone marrow stromal cell coculture. These data suggest that bone marrow stromal cells increase astrocytic survival post-ischemic injury. This protective function might involve the activation of mitogen-activated protein kinase kinase/extracellular signal-regulated kinase and phosphoinositide 3-kinase/threonine protein kinase pathways. Upregulation of brain-derived neurotrophic factor, vascular endothelial growth factor and basic fibroblast growth factor may also contribute to astrocyte survival.

Anaerobiosis↗

PubMed1996

Monoclonal antibody, KK1, recognizes human retinal astrocytes and distinguishes a subtype of astrocytes in mouse brain.

Astrocytes exhibit a diverse morphology and numerous functions in the central nervous system as well as in the retina. In order to obtain markers for the analysis of astrocytes, we prepared monoclonal antibodies that recognized antigens specific to astrocytes. Monoclonal antibody (mAb), designated KK1, reacted with the processes of astrocytes in the nerve fiber layer and the ganglion cell layer in the human retina as detected by indirect immunofluorescence. Normal Müller cells, whose processes are localized vertically in retina, were not labeled by KK1 mAb. In mouse brain, KK1 mAb reacted specifically with astrocytes in the white matter, but not with those in the gray matter. Studies employing a high-resolution confocal laser scanning microscope and double-labeling with KK1 mAb and commercially available anti-glial fibrillary acidic protein (GFAP) mAb (GA5) revealed that KK1 mAb visualized the processes that were not recognized by anti-GFAP mAb (GA5) in both human retina and mouse brain. In cultured mouse astrocytes, KK1 mAb reacted only with anti-GFAP mAb (GA5)-positive cells, but a small percentage of anti-GFAP mAb (GA5)-positive cells were labeled with KK1 mAb. In addition, the subcellular distribution of the KK1 antigen in cultured astrocytes apparently differed from that of GFAP labeled by anti-GFAP mAb (GA5). The antigen that was purified from the normal mouse brain by KK1 mAb-conjugated beads reacted with anti-GFAP mAb(GA5) in immunoblotting. No reactivity of KK1 mAb was observed in immunohistochemical analysis in GFAP -/- mutant mouse brain. These results demonstrate that KK1 mAb specifically recognized an epitope of GFAP that did not react with other anti-GFAP mAb (GA5). Retinal astrocytes and a subtype of astrocytes in the white matter of mouse brain shared the epitope that was recognized by KK1 mAb. KK1 mAb might be a powerful tool to investigate a subtype of astrocytes.

Animals↗

PubMed1994

Vitamin E, ascorbate, glutathione, glutathione disulfide, and enzymes of glutathione metabolism in cultures of chick astrocytes and neurons: evidence that astrocytes play an important role in antioxidative processes in the brain.

GSH, GSSG, vitamin E, and ascorbate were measured in 14-day cultures of chick astrocytes and neurons and compared with levels in the forebrains of chick embryos of comparable age. Activities of enzymes involved in GSH metabolism were also measured. These included gamma-glutamylcysteine synthetase, GSH synthetase, gamma-glutamyl cyclotransferase, gamma-glutamyltranspeptidase, glutathione transferase (GST), GSH peroxidase, and GSSG reductase. The concentration of lipid-soluble vitamin E in the cultured neurons was found to be comparable with that in the forebrain. On the other hand, the concentration of vitamin E in the astrocytes was significantly greater in the cultured astrocytes than in the neurons, suggesting that the astrocytes are able to accumulate exogenous vitamin E more extensively than neurons. The concentrations of major fatty acids were higher in the cell membranes of cultured neurons than those in the astrocytes. Ascorbate was not detected in cultured cells although the chick forebrains contained appreciable levels of this antioxidant. GSH, total glutathione (i.e., GSH and GSSG), and GST activity were much higher in cultured astrocytes than in neurons. gamma-Glutamylcysteine synthetase activity was higher in the cultured astrocytes than in the cultured neurons. GSH reductase and GSH peroxidase activities were roughly comparable in cultured astrocytes and neurons. The high levels of GSH and GST in cultured astrocytes appears to reflect the situation in vivo. The data suggest that astrocytes are resistant to reactive oxygen species (and potentially toxic xenobiotics) and may play a protective role in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1998

Glial fibrillary acidic protein-apolipoprotein E (apoE) transgenic mice: astrocyte-specific expression and differing biological effects of astrocyte-secreted apoE3 and apoE4 lipoproteins.

The epsilon4 allele of apolipoprotein E (apoE) is associated with increased risk for Alzheimer's disease (AD) and poor outcome after brain injury. In the CNS, apoE is expressed by glia, predominantly astrocytes. To define the potential biological functions of different human apoE isoforms produced within the brain, transgenic mice were generated in which human apoE3 and apoE4 expression is under control of the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter. These animals were then bred back to apoE knock-out mice. Human apoE protein is found within astrocytes and the neuropil throughout development and into the adult period, as assessed by immunocytochemistry and immunoblot analysis in several GFAP-apoE3 and E4 lines. Cultured astrocytes from these mice secrete apoE3 and apoE4 in lipoproteins that are high-density lipoprotein-like in size. When primary hippocampal neurons are grown in the presence of astrocyte monolayers derived from these transgenic mice, there is significantly greater neurite outgrowth from neurons grown in the presence of apoE3-secreting astrocytes compared with apoE4-secreting or apoE knock-out astrocytes. These effects are not dependent on direct astrocyte-neuron contact and appear to require the low-density lipoprotein receptor-related protein. These data suggest that astrocyte-secreted, apoE3-containing lipoproteins have different biological effects than apoE4-containing lipoproteins. In addition to providing information regarding the role of astrocyte-secreted apoE lipoproteins in the normal brain, these animals will also be useful in models of both AD and CNS injury.

Animals↗

PubMed2000

Freshly isolated astrocyte (FIA) preparations: a useful single cell system for studying astrocyte properties.

Astrocytes are cell constituents of the mammalian CNS whose intricate relationships with neurons, blood vessels and meninges in situ are well documented. These relationships and their complex morphologies imply numerous functions. Over the past quarter century or so, however, the main experimental basis for determining which roles are likely have been derived from studies on primary astrocyte cultures, usually prepared from neonatal rodent brains. We list a number of examples where these cultures have shown quantitative and qualitative differences from the properties exhibited by astrocytes in situ. The absence of an adequate reliable database makes proposals of likely hypotheses of astrocyte function difficult to formulate. In this article we describe representative studies from our laboratory showing that freshly isolated astrocytes (FIAs), can be used to determine the properties of astrocytes that seem more in concordance with the properties exhibited in situ. Although the cells are most easily isolated from < or =15 day old rat hippocampi they can be isolated from up to 30 day old rats. The examples we describe are that several different types of K(+) currents can be determined by patch clamp electrophysiology, of all the mGluRs only mGluR3 and 5 were detected by single cell RT-PCR, and that single cell Ca(2+) imaging shows that the mGluR5 receptor is functional. It was found that the frequency of cells expressing mGluR5 declines with the age of the animal with the mGluR5b type splice variant replacing the mGluR5a type, as occurs in the intact brain. It is concluded that FIAs can be used to determine the individual characteristics of astrocytes and their properties without the problems of indirect effects inherent in a heterogeneous system such as the slice, and without the problem of cultures unpredictably reflecting the in situ state. The FIAs obviously cannot be used to study interactions of astrocytes with the other CNS components but we propose that they will provide a good database on which hypotheses regarding such interactions can be tested in slices. FIAs can also be isolated from brain slices or intact brain after various pharmacological or electrophysiological perturbations to determine the changes in astrocyte properties that correlate with the perturbations.

Animals↗

PubMed2006

Role of neuronal NR2B subunit-containing NMDA receptor-mediated Ca2+ influx and astrocytic activation in cultured mouse cortical neurons and astrocytes.

The excitatory neurotransmitter glutamate has been shown to mediate such bidirectional communication between neurons and astrocytes. In the present study, we determined the role of N-methyl-D-aspartate (NMDA) receptors on glutamate-evoked Ca(2+) influx into neurons and astrocytes. Either a nonselective NMDA receptor antagonist (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801) or selective NR2B subunit-containing NMDA receptor antagonists ifenprodil and (R,S)-alpha-(4-hydroxyphenyl)-beta-methyl-4-(phenylmethyl)-1-piperid inepropanol (Ro25-6981) significantly inhibited the glutamate-evoked Ca(2+) influx into neurons, but not into astrocytes. Furthermore, we investigated whether NR2B subunit-containing NMDA receptor antagonists could suppress the astrocytic activation, as detected by glial fibrillary acidic protein (GFAP; as a specific marker of astrocyte)-like immunoreactivities in mouse cortical astrocytes. Here, we demonstrated that the increases in the level of GFAP-like immunoreactivities induced by glutamate were markedly suppressed by cotreatment with ifenprodil in cortical neuron/glia cocultures, but not in purified astrocytes. These results suggest that NR2B subunit-containing NMDA receptor plays a critical role in not only glutamate-evoked Ca(2+) influx into neurons, but also glutamate-induced astrocytic activation. Thus, glutamate-mediated pathway via NR2B subunit-containing NMDA receptor may, at least in part, contribute to neuron-to-astrocyte signaling.

Aniline Compounds↗

PubMed1998

Trk A, B, and C are commonly expressed in human astrocytes and astrocytic gliomas but not by human oligodendrocytes and oligodendroglioma.

Neurotrophins regulate the proliferation and differentiation of neurons in the central nervous system via a family of specialized receptors, including TrkA, TrkB, and TrkC. As little is known about their expression or potential role in human glial tissues and glial tumors, we undertook an immunohistochemical analysis of human glia, glioma tissues and cell cultures of glial tumors to characterize the expression of Trk family members (full-length TrkA, TrkB, the truncated form of TrkB, and TrkC). In normal human brain Trk A, B, and C immunoreactivity was found in neurons and some weak staining was also seen astrocytes. No Trk expression was seen on oligodendrocytes. Strong reactivity was seen in reactive astrocytes in a glial scar. In a total of 34 glioma tissue specimens, which included 16 astrocytic tumors (4 low-grade astrocytomas and 12 glioblastomas multiforme) and 15 oligodendrogliomas (8 low-grade and 7 anaplastic) as well as 3 oligoastrocytomas (WHO grade II), TrkA, B, and C immunoreactivity was observed exclusively in specimens from astrocytic gliomas (16/16), but not in any of the oligodendrocytic gliomas (0/15). In the oligoastrocytomas, staining was restricted to the astrocytic component. In the astrocytoma and oligodendroglioma specimens, Trk A, B, and C immunoreactivity was also seen in the surrounding reactive astrocytes. Trk expression was independent of age, sex or histological grade of the investigated tumors. In six primary cell cultures, one derived from human astrocytes and five established from malignant astrocytomas, only TrkA immunoreactivity could be detected, while TrkB (both full-length and truncated isoforms) and TrkC were absent. The TrkA expression in primary cell cultures decreased with continuous cell passaging, and no Trk could be detected in established cell lines derived from glioblastoma. In conclusion, our data suggest that in human glial tissues Trk A, B, and C may be expressed in a lineage-restricted manner, thereby distinguishing between astrocytes and oligodendrocytes in a marker-like fashion. Trk expression, like GFAP expression appears to be increased in activated (reactive)/neoplastic astrocytes.

Adult↗

PubMed2003

Astrocytes accumulate A beta 42 and give rise to astrocytic amyloid plaques in Alzheimer disease brains.

beta-Amyloid(1-42) (A beta 42), a major component of amyloid plaques, accumulates within pyramidal neurons in the brains of individuals with Alzheimer's disease (AD) and Down syndrome. In brain areas exhibiting AD pathology, A beta 42-immunopositive material is observed in astrocytes. In the present study, single- and double-label immunohistochemistry were used to reveal the origin and fate of this material in astrocytes. Our findings suggest that astrocytes throughout the entorhinal cortex of AD patients gradually accumulate A beta 42-positive material and that the amount of this material correlates positively with the extent of local AD pathology. A beta 42-positive material within astrocytes appears to be of neuronal origin, most likely accumulated via phagocytosis of local degenerated dendrites and synapses, especially in the cortical molecular layer. The co-localization of neuron-specific proteins, alpha 7 nicotinic acetylcholine receptor and choline acetyltransferase, in A beta 42-burdened, activated astrocytes supports this possibility. Our results also suggest that some astrocytes containing A beta 42-positive deposits undergo lysis, resulting in the formation of astrocyte-derived amyloid plaques in the cortical molecular layer in brain regions showing moderate to advanced AD pathology. These astrocytic plaques can be distinguished from those arising from neuronal lysis by virtue of their smaller size, their nearly exclusive localization in the subpial portion of the molecular layer of the cerebrocortex, and by their intense glial fibrillary acidic protein immunoreactivity. Overall, A beta 42 accumulation and the selective lysis of A beta 42-burdened neurons and astrocytes appear to make a major contribution to the observed amyloid plaques in AD brains.

Aged↗

PubMed2003

Neurons and astrocytes secrete factors that cause stem cells to differentiate into neurons and astrocytes, respectively.

We examined the role of soluble factors secreted by neurons and astrocytes in the differentiation of CNS stem cells. We showed that the soluble factors from neurons strongly induced multipotent cortical stem cells to acquire neuronal identity, while the factors from astrocytes promoted astrocytic differentiation. Neurons secreted the brain-derived neurotrophic factor and neurotrophin-3 to induce neuron differentiation, while astrocytes secreted ciliary neurotrophic factor for astrocyte differentiation. Both neurons and astrocytes secrete bone morphogenetic proteins (BMPs). Using BMP antagonists it was shown that BMPs were responsible for the neuron-induced neuronal differentiation, as well as the astrocyte-induced astrocytic differentiation. These findings demonstrate the importance of soluble signals in lineage-specific differentiation and provide evidence for the roles of neurons and astrocytes in stem cell differentiation.

Animals↗

PubMed2006

Phosphoprotein enriched in astrocytes-15 kDa expression inhibits astrocyte migration by a protein kinase C delta-dependent mechanism.

Phosphoprotein enriched in astrocytes-15 kDa (PEA-15), a phosphoprotein enriched in astrocytes, inhibits both apoptosis and proliferation in normal and cancerous cells. Here, analysis of PEA-15 expression in glioblastoma organotypic cultures revealed low levels of PEA-15 in tumor cells migrating away from the explants, regardless of the expression levels in the originating explants. Because glioblastomas are highly invasive primary brain tumors that can originate from astrocytes, we explored the involvement of PEA-15 in the control of astrocyte migration. PEA-15-/- astrocytes presented an enhanced motility in vitro compared with their wild-type counterparts. Accordingly, NIH-3T3 cells transfected by green fluorescent protein-PEA-15 displayed a reduced migration. Reexpression of PEA-15 restored PEA-15-/- astrocyte motility to wild-type levels. Pharmacological manipulations excluded a participation of extracellular signal-regulated kinase/mitogen-activated protein kinase, phosphatidylinositol 3-kinase/Akt, and calcium/calmodulin-dependent protein kinase II in this effect of PEA-15. In contrast, treatment by bisindolylmaleimide, Gö6976, and rottlerin, and chronic application of phorbol 12-myristate 13-acetate and/or bryostatin-1 indicated that PKC delta mediated PEA-15 inhibition of astrocyte migration. PEA-15-/- astrocytes constitutively expressed a 40-kDa form of PKC delta that was down-regulated upon PEA-15 reexpression. Together, these data reveal a new function for PEA-15 in the inhibitory control of astrocyte motility through a PKC delta-dependent pathway involving the constitutive expression of a catalytic fragment of PKC delta.

Active Transport, Cell Nucleus↗

PubMed1993

Differences between reactive astrocytes and cultured astrocytes treated with di-butyryl-cyclic AMP.

The long-standing idea that astrogliosis acts as a barrier for regenerating axons could be tested if an in vitro model of reactive astrocytes were available. The morphology and intermediate filament content of cultured perinatal astrocytes treated with di-butyryl-cyclic-AMP are reminiscent of reactive astrocytes evoked by injury. Thus, they have been proposed as a reactive astrocyte in vitro model. However, we show here that di-butyryl-cyclic-AMP-treated astrocytes are much closer to untreated neonatal cells than to reactive astrocytes in vivo, when using other immunohistochemical markers of living reactive glia (i.e. EGF receptor or laminin). Furthermore, living di-butyryl-cyclic-AMP-treated astrocytes and untreated, flat, epithelioid cells, as well as their purified plasma membranes, had similar neurite outgrowth promoting properties, whereas membranes from gliotic tissue enriched in reactive astrocytes inhibited neurite outgrowth. Our observations indicate that di-butyryl-cyclic-AMP treatment leads, at best, to a morphological model of reactive cells that does not share many properties of reactive astrocytes in vivo.

Animals↗

PubMed1997

Lectin histochemistry of astrocytic tumors and in vitro characterization of lectin-induced modifications on the proliferation of the SW1088, U373 and U87 human astrocytic cell lines.

The role of lectins as biosignalling molecules or as markers of human astrocytic tumors remains relatively unexplored. The aim of the present work is to investigate (1) whether or not human astrocytic tumors express specific glycans, evidenced experimentally by means of lectin histochemistry, and (2) whether, in turn, these lectins can significantly modulate astrocytic tumor cell proliferation. Using a cell image processor, we therefore began by quantitatively measuring the histochemical binding pattern of 5 lectins (WGA, PNA, PHA-L, GSA-IA4 and Con A) in 5 astrocytomas, 5 anaplastic astrocytomas and 5 glioblastomas. Secondly, we measured the influence of these 5 lectins on the proliferation of 3 astrocytic tumor cell lines (SW1088, U373 and U87) growing in vitro as monolayers. Cell proliferation was assessed by means of the colorimetric MTT assay. The histochemical lectin staining markedly varied intra- and inter-group. However, some constant results were obtained. Indeed, the staining increased markedly from GSA-IA4 and PHA-L through WGA and PNA to ConA in the three histopathological groups. The assessment of cell proliferation demonstrated that WGA, Con A and PHA-L very significantly decreased proliferation in the 3 astrocytic cell lines in a dose-dependent manner. Astrocytic tumor cells in the confluent growth phase were less sensitive to the WGA, Con A and PHA-L lectin-induced effects than cells in the log growth phase. The GSA-IA4 and PNA lectins had globally very weak effects on the proliferation of the astrocytic tumor cell lines. Increasing the fetal calf serum from 1% to 10% in the culture media significantly antagonized the WGA-, Con A- and PHA-L-induced cell proliferation decrease in the 3 astrocytic cell lines. In conclusion, the present data strongly suggest that some lectins (including WGA, Con A and PHA-L) significantly influence the proliferation of astrocytic tumor cells.

Analysis of Variance↗